Why is Python such a popular language in the AI field?
Python comes with a huge amount of inbuilt libraries. Many of the libraries are for Artificial Intelligence and Machine Learning. Some of the libraries are TensorFlow (which is a high-level neural network library), scikit-learn (for data mining, data analysis and machine learning), pylearn2 (more flexible than scikit-learn), etc. The list keeps going and never ends. You can find some libraries here.
Python has an easy implementation for OpenCV. What makes Python favorite for everyone is its powerful and easy implementation.
For other languages, students and researchers need to get to know the language before getting into ML or AI with that language. This is not the case with Python. Even a programmer with very basic knowledge can easily handle Python. Apart from that, the time someone spends on writing and debugging code in Python is way less when compared to C, C++ or Java. This is exactly what the students of AI and ML want. They don't want to spend time on debugging the code for syntax errors, they want to spend more time on their algorithms and heuristics related to AI and ML
Not just the libraries but their tutorials, handling of interfaces are easily available online. People build their own libraries and upload them on GitHub or elsewhere to be used by others.
All these features make Python suitable for them.